The Pokemon World Tournament is a really cool idea, I would gladly take this over the Battle Frontier anyday, but I feel like they could have done it better, with more trainers.
I would love to see previous E4 members here, since we haven't heard from Lorelei, Agatha and the Hoenn E4 in a long time, (even though we're likely to see the Hoenn Elite when / if they remake RS).
I would also have loved to see previous Rivals like Silver, Wally, etc in the Tournament. Well they technically have one in the form of Blue.
And of course everyone would have loved to see past protaginists. Come on, if Red can come down from his beloved Mountain, Brendan and Lucas and all the others could at least drop by and battle a bit. Then again, I'm pretty sure some hackers will hack them in, replacing other trainers because they can, so that's cool.
One interesting feature is that they will let you download Trainers who top VGC's, correct me if I'm wrong, but I believe it's VGC winners who get programed in the game, or like the Top 8 or something, via Wi-Fi event. That's really cool because obviously, people who make it that far in the tournaments will have very good teams with good movesets (Inb4 some random noob gets really lucky with crappy Pokemon), considering GameFreak aren't the best at creating movesets of their own Pokemon. Although I will admit that they are getting better at making movesets, I was looking through Serebii and some people have Choiced Pokemon. For example, I saw Wattson with a Choice Scarfed Rotom-Wash. That's a standard competitive set right there! I also saw a Choice Banded Ferrothorn, although it isn't used too often in Standard play because regular Leech Seeding hazard set is better anyways, but it's still cool.
I'm really looking forward to the Pokemon World Tournament when Black 2 & White 2 get released in North America. I'm also excited to see what other stuff they can do with it, using Wi-Fi events. :]